Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Antihalation or filter layer containing
Reexamination Certificate
2000-02-23
2002-03-12
Schilling, Richard L. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Antihalation or filter layer containing
C430S517000, C430S523000, C430S527000, C430S533000, C430S534000, C430S535000, C430S536000, C428S481000, C428S483000, C428S500000, C428S515000, C428S532000
Reexamination Certificate
active
06355405
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to multilayer articles, such as radiation-sensitive imaging articles, having two or more layers on a polymeric support. A layer next to the support has a single-phase mixture of polymers that provides multiple properties including adhesion of the layer to the polymeric support. In particular, the invention is directed to photothermographic elements. The invention also relates to a method of preparing the noted articles, including photothermographic elements.
BACKGROUND OF THE INVENTION
Silver halide-containing imaging materials are well known and methods of preparing them have been well known in the industry for decades. Photographic materials are photosensitive silver halide materials that are processed to provide a visible image using conventional liquid processing solutions.
Photothermographic imaging materials and other heat-processable materials (that is materials that are heat-developable and not wet developable) are also well known. These materials are also known in the art as “dry silver” materials and generally comprise a support having coated thereon a photosensitive emulsion comprising a photosensitive silver material, a non-photosensitive, reducible silver source, a reducing agent for silver ions, and a binder.
The photosensitive silver material is generally photographic silver halide that must be in catalytic proximity to the non-photosensitive, reducible silver source. Catalytic proximity requires an intimate physical association of these two materials so that when silver atoms are generated by irradiation or light exposure, those atoms are able to catalyze the reduction of the reducible silver source. Reducible silver sources are generally silver salts of a long chain aliphatic carboxylic acids (such as a behenic or other fatty acid salts).
In both photographic and photothermographic materials, exposure of the photographic silver halide to light produces small clusters of silver atoms that form a latent image in an imagewise fashion. Since the latent image is not visible by ordinary means, it must be further processed to produce a visible image. This is accomplished by reduction of the silver ions. In photothermographic materials, reduction is achieved using the incorporated reducing agent (that is any “developer” that can reduce silver ion to metallic silver). Reduction is then brought about at elevated developing temperatures, producing a black-and-white image of elemental silver.
Because the necessary image-forming chemistry is within the material itself, such materials have a different set of problems that must be addressed. Much effort has been expended in the industry to prepare and manufacture such materials to minimize fog formation upon coating, storage and post-processing aging. Similarly, the unexposed silver halide inherently remains after development and the material must be stabilized after development.
In addition, the binders used in photothermographic elements must be stable for thermal processing and provide both layer cohesion and interlayer adhesion. For example, all coatings usually require a specific range of adhesion with underlying coatings or supports (such as polyester substrates) to meet useful end purposes. The conventional state of the art is to treat the support surface in some manner, such as with electrical corona treatment, flame treatment and glow discharge, to increase wettability and bonding strength. While these treatments do provide increased adhesion, they also leave charge or surface irregularities on the support that result in surface irregularities when an organic solvent based coating is applied. Other disadvantages with such treatments are high inherent capital costs, maintenance and upkeep of the equipment and in some cases the need for inert gases.
Another manner for improving adhesion is to apply a primer layer on the support prior to applying other layers including photosensitive layers. Such coatings include a wide range of formulations, and are usually aqueous in nature to provide the desired adhesion to subsequent layers. These methods are generally inadequate when organic solvent-based coatings are applied to the primer layer due to poor adhesion and/or migration of the components from the primer layer into upper layers. These result in a variety of unwanted physical (for example, product discoloration, haze, static discharge, gels, and poor coating quality) or chemical (for example, dye fade and sensitometric effects) effects.
WO 96/15478 (Geisler et al) and U.S. Pat. No. 5,928,857 (Geisler et al) describe IR-sensitive photothermographic elements having improved adhesion using additional adhesive materials in the photosensitive layer. Thus, besides the usual polyvinyl butyral binder, the photosensitive layer also includes a polymeric component that is not a polyvinyl acetal. This polymeric component has a higher strength of adhesion to polyester film than a polyvinyl acetal and the improved adhesion is readily observed in high-density image areas.
Primer layers for photothermographic materials are described for example in U.S. Pat. No. 4,752,559 (Helland et al) to include a pigmented acrylic polymer binder system. This binder system is said to adhere to a photosensitive layer containing a variety of polymer binders including polyvinyl acetals. Polymeric substrates can also be coated with a polyacrylate/gelatin composition that either adheres the photosensitive layer to the substrate or includes the photosensitive materials, as described in U.S. Pat. No. 5,244,780 (Strobel et al).
Block and graft copolymers are described as adhesion promoting materials in U.S. Pat. No. 5,384,192 (Long et al) between the support and the organic polymer layer (photosensitive layer). The copolymers have a component compatible with the organic polymer layer and a poly(vinyl phenol). Other more complicated polymer subbing layer materials are described in U.S. Pat. No. 5,639,589 (Bauer et al).
The use of primer layers may be necessary in some instances, but as noted above, their use presents a number of problems. In addition, they require additional coating passes, capital investment and film waste. Curl may also result from application of the additional layer.
There are several known techniques for simultaneous coating of multiple layers. For example, U.S. Pat. No. 4,001,024 (Dittman et al) describes what is known in the industry as “slide” coating technology in which a plurality of thin layers are applied to a moving web (support) to prepare photographic elements. This technology is best used with the lowermost layer being thinner (wet thickness) than the upper layers. This thinner layer has become known as a “carrier” layer and can be chosen from a wide range of materials that are compatible with the silver/gelatin containing photosensitive layers coated on top so that interlayer mixing can occur without adverse effect.
Thin “accelerating” or carrier layers are described in U.S. Pat. No. 4,569,863 (Koepke et al) for use in what is known as “curtain” coating methods for preparing multilayer photographic elements. Still other coating techniques are described in U.S. Pat. No. 4,572,849 (Koepke et al) in which thin accelerating layers are composed of various hydrophilic coating materials. In U.S. Pat. No. 5,641,544 (Melancon et al), U.S. Pat. No. 5,733,608 (Kessel et al), U.S. Pat. No. 5,849,363 (Yapel et al) and U.S. Pat. No. 5,861,195 (Bhave et al) thin “carrier fluids” and coating fluids are described as comprising non-miscible materials. The carrier layers applied in these procedures are used for some aspect of coating quality such as streak reduction, reducing air entrapment, increased line speed and reduction in “strike through”.
While WO 96/15478 and U.S. Pat. No. 5,928,857 (both noted above) describe an advance in the art to adhere photothermographic imaging layer to polyester supports, there is a desire to avoid adding additional components, particularly additional binders, to the imaging layers. Yet, polyvinyl butyral, the most common binder does not satisfactorily bind the imag
Bhave Aparna V.
Crump Anne E.
Geisler Thomas C.
LaBelle Gary E.
Ludemann Thomas J.
Schilling Richard L.
Tucker J. Lanny
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